(1) Field of the Invention
The present invention relates to a ring network concentrator for connecting between independent ring networks, and building a network system from the ring networks.
(2) Description of the Related Art
A ring network is frequently employed for a high-speed data communication. A local area network is an example of such ring network. This type of ring network, a FDDI (Fiber Distributed Data Interface) which provides a data transmission rate of 100 mega bit per second (Mbps) over fiber-optic cables, has become an ISO standard recently, i.e. ISO9314. The FDDI 93014 is defined by a PHY (Physical Medium Dependent), an MAC (Media Access Control), a PMD (Physical Medium Dependent), and a SMT (Station Management). Among these components, only the SMT is still under discussion, and an ANSI (American National Standards Institute) Draft Proposed X3T9/1992-067 FDDI SMT Rev 7.2 has been issued so far.
The typical configuration of a ring network system basing upon the FDDI will be discussed. The FDDI carries out a high-speed packet communication as a trunk network, and a packet relay device, such as Ethernet accommodates a branch network for carrying out a low-speed packet communication. Conventionally, the FDDI is connected to the packet relay device, and terminal stations are connected to the branch network.
Because of a recent development in performance of a terminal station, a high speed data communication is demanded even at a multi-media application, such as image data or voice data. To meet this demand, a concentrator for directly linking terminal stations to the FDDI is required.
The capabilities and design of the FDDI concentrator is described in "Michael Franzen, FDDI concentrators and how they work together with other FDDI network components, Computer Networks and ISDN Systems 23 (1991), p. 51-55). In the Franzen's article, the basic internal configuration of the FDDI concentrator is determined in accordance with the SMT (Station Management) of ISO9314. More specifically, the FDDI concentrator is constructed from internal paths, ports, MACs (Media Access Control), and configuration switches. The internal paths include three internal paths, i.e. a primary path, a secondary path, and a local path, to send a packet.
The ports include a peer port which is associated with dual rings of a ring trunk network, and a master port which is associated with a single ring of a ring branch network, and a packet is sent on/received from the ring network. Each MAC performs a transmission/reception of packet data, and a ring management. One configuration switch is provided for each port and MAC. The configuration switch decides a connection pattern between ports, MACs, and internal paths to establish a communication channel. Although it is described in the Franzen's article that an MAC is directly inserted into an internal path, this has been changed in that a configuration switch is prepared for each MAC since the introduction of FDDI SMT Rev 7.2. To build a ring network system, the user of the FDDI concentrator presets a connection pattern at each configuration switch indicating which internal path to be connected with the port and the MAC. Thus, the user can set a connection between ring networks and internal paths in the FDDI concentrator, and placement of MACs at will. Therefore, the design of a ring network system can be set freely.
However, the conventional ring network concentrator has a drawback. As stated in the above, a connection pattern at each configuration switch is set beforehand. However, this does not always meet a dynamic change in the ring network which occurs in a moment.